The present invention pertains to change speed gear mechanisms of the type that find particular utility in driving agricultural tractors or the like. These tractors should preferably be able to be inched along at lower speed and otherwise have a wide range of speed ratios. These tractors also have a power take-off shaft for driving auxiliary machinery and the inadvertent operation of these power take-off shafts or the inability to modulate the speed thereof has resulted in shortcomings of prior art transmissions of this general character.